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Proxima Centauri c

Coordinates: Sky map 14h 29m 42.9487s, −62° 40′ 46.141″
From Wikipedia, the free encyclopedia
Proxima Centauri c
Schematic: Orbits of Proxima Centauri d, Proxima Centauri b and Proxima Centauri c around Proxima Centauri
Discovery[1]
Discovered byDamasso et al.
Discovery siteHARPS
Discovery dateJanuary 2020
Radial velocity
Orbital characteristics
1.489±0.049 AU[2]
Eccentricity0.04±0.01[3]
1928±20 d[3]
Inclination133±1[3]
331±1[3]
−4±4[3]
2456202±21[3]
Semi-amplitude1.1±0.2[3]
StarProxima Centauri
Physical characteristics
Mass7±1 M🜨[3]
Temperature39 K (−234.2 °C; −389.5 °F)[1]

Proxima Centauri c (also called Proxima c[2] or Alpha Centauri Cc) is a controversial exoplanet candidate, claimed to be orbiting the red dwarf star Proxima Centauri, which is the closest star to the Sun and part of a triple star system. It is located approximately 4.2 light-years (1.3 parsecs; 40 trillion kilometres; 25 trillion miles) from Earth in the constellation of Centaurus. If existing, this makes it, along with Proxima b and Proxima d, the closest known exoplanets to the Solar System.

Characteristics

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As originally proposed, Proxima Centauri c would be a super-Earth or mini-Neptune about 7 times as massive as Earth, orbiting at roughly 1.49 AU (223 million km; 139 million mi) every 1,928 days (5.28 yr).[3] Due to its large mass and its distance from Proxima Centauri, the exoplanet would be uninhabitable and too cold for liquid water to exist on the surface, with an equilibrium temperature of approximately 39 K (−234.2 °C; −389.5 °F).[1][4] According to a 2025 study, the originally proposed planet most likely does not exist, but there may be a smaller planet with a similar orbit.[5]

The planet does not transit its parent star from the point of view of an Earth-based observer.[6]

Discovery

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The planet candidate was first reported by Italian astrophysicist Mario Damasso and his colleagues in April 2019. Damasso's team had noticed minor movements of Proxima Centauri in the radial velocity data from the ESO's HARPS instrument, analyzed earlier by Ukrainian astrophysicist Yakiv Pavlenko and his colleagues at the Instituto de Astrofísica de Canarias,[7][8][9] indicating a possible second planet orbiting Proxima Centauri.[10] The discovery was published on 15 January 2020.[1]

Subsequent studies in 2020 also found evidence for Proxima c via astrometry,[2] including Hubble data from c. 1995, allowing its inclination and true mass to be determined.[3] Also in June 2020, a possible directly imaged counterpart of Proxima c was detected in the infrared with SPHERE, but the authors admit that they "did not obtain a clear detection".[11] If their candidate source is in fact Proxima Centauri c, it is too bright for a planet of its mass and age, implying that the planet may have a ring system with a radius of around 5 RJ.[11] At the time, the multiple lines of evidence appeared to confirm the planet.[12]

However, a 2022 study questioned the planetary nature of the observed radial velocity signal corresponding to Proxima c, whose detection could not be recreated, attributing it to systematic effects.[13] As of 2025, evidence for Proxima c remains inconclusive; observations with the NIRPS spectrograph were unable to confirm it, but found hints of a lower-amplitude signal, different from the originally proposed planet, with a similar period.[5]

See also

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References

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  1. ^ a b c d Damasso, Mario; et al. (January 2020). "A low-mass planet candidate orbiting Proxima Centauri at a distance of 1.5 AU". Science Advances. 6 (3): eaax7467. Bibcode:2020SciA....6.7467D. doi:10.1126/sciadv.aax7467. PMC 6962037. PMID 31998838.
  2. ^ a b c Kervella, Pierre; Arenou, Frédéric; Schneider, Jean (March 2020). "Orbital inclination and mass of the exoplanet candidate Proxima c". Astronomy & Astrophysics. 635: L14. arXiv:2003.13106. Bibcode:2020A&A...635L..14K. doi:10.1051/0004-6361/202037551. S2CID 214713486.
  3. ^ a b c d e f g h i j Benedict, G. Fritz; McArthur, Barbara E. (June 2020). "A Moving Target—Revising the Mass of Proxima Centauri c". Research Notes of the AAS. 4 (6): 86. Bibcode:2020RNAAS...4...86B. doi:10.3847/2515-5172/ab9ca9. S2CID 225798015.
  4. ^ "A new super-Earth may orbit the star next door". Science. 2020-01-15. Retrieved 2024-10-16.
  5. ^ a b Suárez Mascareño, Alejandro; Artigau, Étienne; et al. (29 July 2025). "Diving into the planetary system of Proxima with NIRPS: Breaking the metre per second barrier in the infrared". Astronomy & Astrophysics. 700: A11. doi:10.1051/0004-6361/202553728.
  6. ^ Gilbert, Emily A.; Barclay, Thomas; Kruse, Ethan; Quintana, Elisa V.; Walkowicz, Lucianne M. (2021), "No Transits of Proxima Centauri Planets in High-Cadence TESS Data", Frontiers in Astronomy and Space Sciences, 8: 190, arXiv:2110.10702, Bibcode:2021FrASS...8..190G, doi:10.3389/fspas.2021.769371
  7. ^ Pavlenko, Ya. V.; Suárez Mascareño, A.; Zapatero Osorio, M. R.; Rebolo, R.; Lodieu, N.; Béjar, V. J. S.; González Hernández, J. I.; Mohorian, M. (June 2019). "Temporal changes of the flare activity of Proxima Centauri". Astronomy & Astrophysics. 626: A111. arXiv:1905.07347. doi:10.1051/0004-6361/201834258. ISSN 0004-6361.
  8. ^ "Проксима Центавра може бути домом для другої планети [оновлено]". scienceukraine.com (in Ukrainian). 16 January 2020. Archived from the original on 2020-09-23. Автори використали наші результати, отримані у співпраці з групою вчених з Інституту астрофізики на Канарських о-вах, для того, щоб відкинути можливість пояснення довгоперіодичної варіації параметрів спектру Проксими явищами зоряної активності.
  9. ^ "Проксима Центавра може бути домівкою для ще однієї землеподібної планети". www.old.nas.gov.ua (in Ukrainian). Retrieved 2024-10-29.
  10. ^ Billings, Lee (April 12, 2019). "A Second Planet May Orbit Earth's Nearest Neighboring Star". Scientific American. Retrieved April 12, 2019.
  11. ^ a b Gratton, R.; et al. (June 2020). "Searching for the near-infrared counterpart of Proxima c using multi-epoch high-contrast SPHERE data at VLT". Astronomy & Astrophysics. 638: A120. arXiv:2004.06685. Bibcode:2020A&A...638A.120G. doi:10.1051/0004-6361/202037594. S2CID 215754278.
  12. ^ Benedict, Fritz (June 2, 2020). "Texas astronomer uses 25 year-old Hubble data to confirm planet Proxima Centauri c". McDonald Observatory. University of Texas.
  13. ^ Artigau, Étienne; Cadieux, Charles; Cook, Neil J.; Doyon, René; Vandal, Thomas; et al. (June 23, 2022). "Line-by-line velocity measurements, an outlier-resistant method for precision velocimetry". The Astronomical Journal. 164:84 (3) (published August 8, 2022): 18pp. arXiv:2207.13524. Bibcode:2022AJ....164...84A. doi:10.3847/1538-3881/ac7ce6.
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